The invention is directed to the production of monoperoxydicarboxylic acids and their salts.
It has long been known to use these compounds as bleaching agents in washing compositions.
There is described in Australian Patent No. 417,480 the improved bleaching action of monoperoxyphthalic acid in the present Mg.sup.2+ ions in the bleach liquor. The French Patent No. 2,129,034 is directed to the production of stable monoperoxyphthalic acid from phthalic anhydride and hydrogen peroxide in the presence of 0.01 to 1 mole of magnesium oxide per mole of anhydride. The magnesium salt of the peracid is formed at least in part therefrom and the peracid is precipitated by the addition of a strong mineral acid.
An alkaline acting magnesium compound likewise is necessary according to European patent No. B1-0027693 in order to carry out the oxidation of phthalic anhydride with hydrogen peroxide and simultaneously obtain the magnesium salt of the monoperoxyphthalic acid.
The production of monomperoxyphthalic acid is described in the Acta Chem. Scand. Vol. 12 (1958) 6, page 1331. In order to attain sufficient yield, it is necessary to react the phthalic anhydride at a temperature of below -5.degree. C. with the alkaline oxidation solution. The peracid is separated off after treatment of the solution with sulfuric acid and water by extraction with ether.
The object of the invention is to develop a process of obtaining monoperoxydicarboxylic acids and their salts in a simple manner.